The present invention relates to a process for producing a fiber-reinforced plastic part.
For some time, BMW AG has been working on processes for the series production of carbon-fiber-reinforced vehicle body components. In the production of vehicle body parts, a reinforcing matrix is frequently used, which consists of a fiber material and is placed in an injection molding tool where a liquid thermosetting resin is sprayed around it. The liquid thermosetting resin saturates the reinforcing matrix. The reinforcing matrix is a “mat-type” formation, for example, in the shape of a woven material, a scrim, a knit, a crocheted material, or the like.
In the vehicle body construction field, the so-called “mixed construction”, i.e. the connection of components consisting of different materials, for example, of carbon-fiber-reinforced plastic components with steel or aluminum components, presents a considerable challenge. Gluing represents one possibility of connecting such different materials with one another.
As an alternative, fiber-reinforced plastic parts and metal parts may also be mutually connected by way of form-locking connection elements, which, however, frequently requires that at least one of the two components to be connected with one another has a passage hole. Passage holes should, however, be avoided, if possible, for reasons of stability, among others, in the case of fiber-reinforced plastic components.
It is an object of the invention to provide a process for producing a fiber-reinforced plastic part, which can be connected in a simple manner with other components without requiring any perforation of the plastic part to be produced.
This and other objects are achieved by a process for producing a fiber-reinforced plastic part, the process including the acts of: providing a mat-type reinforcing matrix comprised of a fiber material, inserting the reinforcing matrix into a tool, particularly an injection molding tool, and closing the tool, wherein in a connection area, in which the plastic part to be produced is to be connectable later with a further component, the reinforcing matrix is deformed such that a trough-type bulging-out is formed, a place holder element being inserted into the bulging-out, and the bulging-out being filled up with plastic material around the place holder element.
The starting point of the invention is a process for producing a fiber-reinforced plastic part, in which case a mat-type reinforcing matrix comprised of fiber material is used for stiffening the plastic part to be produced. The “fibers” contained in the reinforcing matrix may, for example, be carbon fibers, glass fibers, metal wires, or the like or combinations of various fiber types. The mat-type formation, i.e. the reinforcing matrix, may be present in the form of a woven material, a scrim, a knit, a crocheted material, or the like, or in combinations of such structures.
In a first step, the mat-type reinforcing matrix is placed in a tool. The tool is a resin transfer molding tool. Such a tool consists, for example, of a tool bottom part and a tool top part that can be moved relative thereto, which, between one another, form a mold cavity corresponding to the geometry of the plastic parts to be produced. After the placing of the reinforcing matrix, the molding tool will be closed. A liquid thermosetting plastic material will then be injected, which fills up the mold cavity and saturates the reinforcing matrix. The tool can be heated in the process. In particular, the plastic material may be a thermosetting synthetic resin.
As an alternative to the use of an injection molding tool, by which liquid plastic material is injected into a cavity of the tool, it may also be provided that a stiffening matrix saturated, coated or surrounded by a thermosetting starting material is used as the starting material or that the reinforcing matrix is painted outside the tool, for example, manually, with such a plastic material, or plastic material is applied in a different manner to the reinforcing matrix and that the reinforcing matrix is subsequently introduced into a (wet-pressing) tool and reshaped into a plastic part.
An aspect of the invention is that the reinforcing matrix is bulged out in a trough-type manner in a “connection area”, i.e. in an area in which the plastic part to be produced is to be connected later with a further component. For this purpose, the injection molding tool or the top or bottom tool has a corresponding bulging-out or bulging-in in the connection area. A “space holder element” is placed into the trough-type bulging-out of the reinforcing matrix before the injection of the plastic material. Subsequently, the mold cavity including the trough-type bulging-out is filled up with liquid plastic. The “place holder element” has the task of keeping a predefined area of the plastic part to be produced free of plastic material.
According to a further development of the invention, the place holder element will be removed from the created plastic part after the setting of the plastic material.
This results in a cup-type indentation in the plastic part at the point at which the place holder element had been situated. Subsequently, a connection element can be inserted into this cup-type indentation by way of which the plastic part is connected with a further component, for example, with a (further) vehicle body component.
After the setting of the plastic material, the place holder element can, for example, simply be pulled out of the indentation.
As an alternative, a place holder element may also be used on whose outer circumference a thread is provided, so that, when the bulging-out is filled up with plastic material, a cup-shaped indentation is obtained which has a corresponding mating thread. After the setting of the plastic material, the place holder element can be unscrewed from the mating thread, so that a cup-shaped indentation is obtained which is provided with the mating thread. A cup-type indentation having a thread has the advantage that a connection element provided with a corresponding thread can be screwed directly into the cup-type indentation or into the mating thread of the cup-type indentation, whereby a high connection stability can be achieved. The connection element can additionally be glued into the cup-type connection, whereby a still higher connection stability can be achieved. A connection element can naturally also be glued into a cup-type connection which has no thread.
According to a further development of the invention, a connection element is used which has a head projecting from the cup-type indentation. The head may, for example, have a multi-edged shape. As an alternative, the head may also completely or partially have the shape of a sphere or completely or partially have a shape similar to a sphere. A spherical head or a head similar to a sphere has the advantage that a snap-on element can be snapped onto it in a simple manner, which snap-on element is part of an additional component to be connected with the plastic part. In contrast to angular connection elements, spherical-head-type connection elements or connection elements similar to a spherical head have the advantage that a catching or jamming of a snap-on element interacting with the latter will be almost impossible.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.